Topic
Deltatheroida
About: Deltatheroida is a research topic. Over the lifetime, 15 publications have been published within this topic receiving 771 citations.
Papers
TL;DR: Dental evidence supports the monophyly of higher (tribosphenic) mammals and suggests that the predominantly Old World Deltatheroida, recently proposed as a sister taxon to marsupials, represents a primitive and unrelated group of higher mammals.
Abstract: A mammal from the Early Cretaceous of the western United States, represented by a lower jaw exceptional in its completeness, presents unambiguous evidence of postcanine dental formula in an Early Cretaceous marsupial-like mammal, and prompts a reconsideration of the early evolution of marsupial dental characters. A marsupial postcanine dental formula (three premolars and four molars) and several marsupial-like features of the lower molars are present in the new taxon, but a hallmark specialization of marsupials (twinning of the hypoconulid and entoconid on lower molars) is lacking. This, coupled with recent evidence from the Late Cretaceous of the western United States, suggests that the distinctive marsupial dental formula evolved prior to the most characteristic specialization of lower molars and that apomorphies presumed to be diagnostic of the upper molars (such as auxiliary stylar cusps) were relatively more recent developments in marsupial history. Dental evidence supports the monophyly of higher (tribosphenic) mammals and suggests that the predominantly Old World Deltatheroida, recently proposed as a sister taxon to marsupials, represents a primitive and unrelated group of higher mammals; by this interpretation, early marsupials and their presumed close relatives are restricted to North America. This, together with the hypothesized relationships of South American/Australian marsupials (in the context of the North American Cretaceous radiation) and evidence from the fossil record of South America, in turn supports a North American origin for the group.
101 citations
TL;DR: The Deltatheroida have at least an incipient alisphenoid bulla, three premolars sharply differentiated morphologically from four molars, a very large stylar area and the protoconid higher than the metaconid.
Abstract: A lower molar of Sulestes sp., a deltatheridiid from the Coniacian of Uzbekistan, is described. The Deltatheroididae new fam. is erected. The Deltatheroididae and Deltatheridiidae are assigned to the order Deltatheroida Kielan-Jaworowska 1982 and it is argued that the Deltatheroida are metatherians, a sister group of Marsupialia. The Deltatheroida have at least an incipient alisphenoid bulla, three premolars sharply differentiated morphologically from four molars, a very large stylar area and the protoconid higher than the metaconid. They differ from known Cretaceous marsupials in having a tendency to lose the last molar, in having a small protocone, a narrow and short talonid, and a hypoconulid and entoconid not approximated. Known deltatheroidan taxa are compared. Relationships of the Deltatheroida and Aegialodontia are discussed. The place of metatherian origin is still not known with certainty. □Mammalia, Metatheria, Deltatheroida, Marsupialia, Cretaceous, Asia, Paleobiogeography.
72 citations
TL;DR: The stumbling block in establishing mono‐ or polyphyletic origins of mammals is the uncertain position of the Haramiyidae (the oldest Multituberculata, and possibly the oldest mammals), known only from isolated teeth.
Abstract: Polyphyletic or monophyletic origins of mammals have been subjects of considerable controversy for a century. Late Triassic—Early Jurassic mammals are more diverse than previously thought. The stumbling block in establishing mono‐ or polyphyletic origins of mammals is the uncertain position of the Haramiyidae (the oldest Multituberculata, and possibly the oldest mammals), known only from isolated teeth. Triconodonta and Theria probably shared an unknown common ancestor, while Monotremata possibly branched from early Eupantotheria at the end of the Early Jurassic, before the Dryolestoidea did, from the forms in which the cochlea started to coil and small cerebellar hemispheres developed. Aegialodontia gave rise to Metatheria but not to Eutheria. Deltatheroida belongs to Metatheria. A group of Cretaceous therian mammals with tribosphenic molars informally classified as “Tribotheres”; cannot be assigned either to Metatheria or Eutheria.
48 citations
TL;DR: The analysis confirms the monophyly of the Hathliacynidae ( Notogale, Cladosictis, Sallacyon ,, and Sipalocyon )) but definitely excludes Mayulestes from the family.
47 citations
TL;DR: A reassessment of Early Cretaceous mammals with tribosphenic molars shows that metatherians and eutherians apparently evolved independently from a peramuran-like ancestor, and an entoconid.
Abstract: A cladistic analysis of the major groups of early metatherian mammals shows that the Deltatheroida and South American dog-like Borhyaenoidea are closely related and are placed in a new supercohort Deltatheralia. while all other metatherians are placed in the supercohort Marsupialia. A reassessment of Early Cretaceous mammals with tribosphenic molars shows that metatherians and eutherians apparently evolved independently from a peramuran-like ancestor, and an entoconid. distinctly basined talonid and large protocone were acquired separately in each group. Consequently. the Tribosphenida (sensu McKenna) is apparently paraphyletic. Aegialodontia are regarded as structurally ancestral to Metatheria but not Eutheria. The known fossil record supports the view that differentation of the stocks which gave rise to metatherians and eutherians apparently occurred in Late Jurassic or Early Cretaceous time.
43 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2016 | 1 |
| 2015 | 1 |
| 2014 | 1 |
| 2010 | 1 |
| 2009 | 1 |
| 2008 | 1 |